Update PSUseCorrectCasing to enforce correct casing of automatic variables

[xtqqczze]

Summary of the new feature

Incorrect case of automatic variables should result in a PSUseCorrectCasing rule violation.

Proposed technical implementation details (optional)

Code using $error should result in a rule violation

Replacement with $Error should be suggested as a fix.

What is the latest version of PSScriptAnalyzer at the point of writing

1.18.3

[bergmeister]

Certainly possible. Would we take the union of automatic variables from Windows PowerShell and PowerShell Core?

[xtqqczze]

There should only be rule violations for automatic variables present in the test environment. We can access a list of special variables at runtime by reflection:

[ref].
Assembly.
GetType('System.Management.Automation.SpecialVariables').
DeclaredFields.
Where{ $PSItem.FieldType -eq [string] }.
ForEach{ $PSItem.GetValue($null) }

https://github.com/SeeminglyScience/EditorServicesCommandSuite/blob/master/module/Classes/Utility.ps1